Influence of steroid ovarian hormones and calcium on drug-induced contractions of the isolated immature uterine muscle of mouse. An analysis of histamine receptor system.

1. Through the relative responsiveness (rho) determined for histamine (Hist), oxytocin (Oxy) and acetylcholine (Ach) in prepuberal untreated, estrogen, and estrogen plus progesterone dominated uteri of mouse, it was possible to measure the capability of each receptor system, which mediates responses induced by these agonists. 2. In all cases values of rho for Hist were lower than those for Ach and Oxy independently of hormone treatment and calcium concentrations used (0.2 or 2.0 mM), suggesting that the ability of histamine receptor system to promote contraction of mouse uterus is less effective than those mediating responses induced by other agonists studied here. 3. A comparison between the present data with those previously reported for dog uterus showed marked differences in the abilities of the histamine receptor system to mediate histaminergic stimulus in myometrium of two different animal species. 4. The author suggests that genetic characteristics controlling the development of a given receptor system can play a role regulating physio-pharmacological actions of drugs in the myometrium.